Generally, electrophoresis involves the migration of sample components through a medium (usually a gel) under the influence of an electric field. Electrophoresis is typically carried out in glass tubes containing rods of gel, although slab gels or paper are also used as solid supports. Electrophoresis is often used for the separation and analysis of proteins and nucleic acids. Isoelectrofocusing, a particular type of electrophoresis, is mainly used for proteins.
A typical apparatus for tube gel electrophoresis consists of a series of glass tubes mounted vertically through sealing rubber grommets into the floor of a box-like electrode-containing buffer chamber (the upper chamber). This chamber is filled with an electrode buffer once all holes in the floor are sealed with gel tubes or blanks. The lower ends of the gel tubes extend into a second buffer chamber (the lower chamber) containing a second electrode. When a voltage is applied between the upper and lower electrodes, a current flows through the tube gels.
In this type of apparatus liquid is prevented from flowing out of the upper chamber by the gel-containing tubes inserted into the tight fitting rubber grommets. An individual tube cannot be removed from the apparatus without first removing the buffer from the upper chamber. Thus, this type of apparatus is inappropriate when it is desired that individual tubes be introduced or removed at different times during electrophoresis.
Even if it is desired that all samples be run in parallel for the same duration of time, it is often not possible with these traditional systems to treat all samples identically. Loading of the gels requires a finite amount of time, therefore samples loaded first and those loaded last have not been treated identically even though the electrophoresis time might be identical. Thus, there is a need in the art for a system in which all tubes are handled individually and sequentially. There is a need for a system in which each individual sample can be handled in exactly the same way. In addition, there is a need in the art for an apparatus which is amenable to being operated automatically.